1. Field of the Invention
This invention relates to a process for producing a 1,3-dialkyl-2-imidazolidinone expressed by the formula (2) ##STR3## wherein R represents --CH.sub.3, --C.sub.2 H.sub.5, --C.sub.3 H.sub.7 or --C.sub.4 H.sub.9, by reacting a N,N'-dialkylethylenediamine expressed by the formula (1) ##STR4## wherein R is as defined above, with urea.
1,3-Dialkyl-2-imidazolidinones expressed by the formula (2) such as 1,3-dimethyl-2-imidazolidinone are very useful substances as a polar, non-protonic solvent. In particular, they are an excellent solvent for various high molecular substances such as polyamides, polyvinyl chloride, polyvinyl alcohol, polystyrene, polyurethane, phenolic resins, etc. Further, they are a useful substance which forms a complex with many inorganic salts and dissolves, and also is used as a solvent for many organic reactions.
2. Description of the Prior Art
Among 1,3-dialkyl-2-imidazolidinones, 1,3-dimethyl-2-imidazolidinone (hereinafter abbreviated to DMI) is a generally well known compound, and as to the process for producing it, various proposals have been made.
For example, a process wherein ethylenediamine is reacted with urea to obtain 2-imidazolidinone (ethylene-urea) which is subjected to addition reaction to formalin, followed by reducing the resulting reaction product with trichloroacetic acid, formic acid or the like, into the corresponding N,N'-dimethyl compound; a process having improved the above reduction process wherein hydrogenation is carried out using a noble metal catalyst in an acidic state; a process wherein N,N'-dimethylethylenediamine is reacted with phosgene or trichloromethyl chloroformate while it is decomposed into phosgene, etc. have been known. Further, a report has been made that N,N'-dimethylethyleneamine is reacted on heating with urea to form 1,1'-dimethyl-1,1'-dimethylenebisurea ##STR5## as an intermediate, which is then heated to above 300.degree. C. to obtain DMI with a yield of 35% (Journal of the Chemical Society (Perkin Trans.) 2, (1981), 317-319).
As described, the process for producing 2-imidazolidinone by reacting ethylenediamine with urea has so far been industrially possible, but it is not easy to dialkylate the above 2-imidazolidinone into 1,3-dialkyl-2-imidazolidinone. Further, in the case of production of DMI by reacting N,N'-dimethylethylenediamine with urea, the yield is so low as described in the above literature that the process has been commercially unsatisfactory at all.
Thus if the objective compound can be produced directly from N,N'-dialkylethyleneamine and urea with a good yield, such a process is a very simple one.